1. Field of the Invention
The present invention relates to a wafer thermometer, temperature measuring device, a heat treatment device, and a method for measuring temperature of a heat treatment unit.
2. Discussion of the Background
In a photolithography step in producing a semiconductor device, various kinds of heat treatments such as a heating process (pre-baking) after applying a resist liquid to a surface of a semiconductor wafer (referred to as the “wafer” hereinafter), a heating process (post exposure baking) after exposing a pattern, and a cooling process performed after each heating process are performed by a heating/cooling device in which the wafer is maintained at a predetermined temperature.
FIG. 8 is a longitudinal sectional view showing a conventional heating/cooling device 60, and FIG. 9 is a transverse sectional view taken along line A-A in FIG. 8.
Referring to FIG. 8, a cooling plate 61 for a cooling process and a heating plate 62 for a heating process are provided in line in a case 90 of the heating/cooling device 60. Each of the cooling plate 61 and the heating plate 62 is in a form of a disk having a certain thickness. A peltiert element (not shown) is incorporated in the cooling plate 61 to cool the cooling plate 61 to a predetermined temperature.
In addition, an elevator pin 63 for supporting and elevating a wafer after the wafer is set on the cooling plate 61 is provided under the cooling plate 61. This elevator pin 63 can be vertically moved by an elevator driving mechanism 64, and penetrates the cooling plate 61 from the bottom of the cooling plate 61 so as to project to the cooling plate 61.
Meanwhile, a heater 65 and a heating plate temperature sensor 62a are incorporated in the heating plate 62, and a controller 66 controls a heat value of the heater 65 based on a temperature detected by the heating plate temperature sensor 62a to maintain the temperature of the heating plate 62 at a set temperature. An elevator pin 67 and an elevator driving mechanism 68 are provided under the heating plate 62 similar to the cooling plate 61, and the wafer can be set on the heating plate 62 by the elevator pin 67.
In addition, as shown in FIG. 9, a carrying device 69 for transporting the wafer to the heating plate 62, and carrying the wafer from the heating plate 62 to the cooling plate 62 is provided between the cooling plate 61 and the heating plate 62. An opening 70 is provided on a side of the cooling plate 61 in the case 90 of the heating/cooling device 60 to take the wafer in and out of the heating/cooling device 60.
A shutter 71 is provided at the opening 70 to maintain an atmosphere in the heating/cooling device 60 at a predetermined atmosphere. A carrying arm 80 is provided so as to be opposed to the shutter 71, and when the shutter 71 is opened, the wafer is carried from the opening 70 into the heating/cooling device 60 by the carrying arm 80, and set on the heating plate 62 by the carrying device 69.
According to this heating/cooling device 60, it is important to previously measure a temperature distribution of the processing wafer set on the heating plate 62 to find temperature characteristics thereof on the heating plate 62, and uniformly heat the wafer on the heating plate 62 by appropriately correcting the temperature distribution based on a measurement result. Conventionally, in order to measure the temperature distribution of the processing wafer on the heating plate 62, the temperature distribution of the wafer is found by a wafer thermometer before the processing wafer is processed, and the temperature distribution of the processing wafer is corrected.
According to the wafer thermometer, the temperature measuring wafer is divided to a plurality of regions, and each of the temperature sensor and a transmitting device is arranged in each region. Data detected by the temperature sensors is transmitted by wireless, and the transmitted data is received by a receiving device provided in or outside the heating/cooling device 60. The transmitting device includes an A/D converter circuit, a memory, a transmitter circuit. However, since the A/D converter circuit has characteristics of being reduced in conversion accuracy as the temperature is increased, although the A/D converter circuit can measure the temperature up to 150° C., it cannot be used in an atmosphere in which the temperature reaches 250° C.
Thus, according to a temperature measuring wafer disclosed in Japanese Unexamined Patent Publication No. 2007-178253, a storage chamber is formed of an insulating material made of nano-crystal silicon (nc-Si) layer around it, and an A/D converting circuit, a memory, and a transmitting circuit are stored in the storage chamber.
However, according to the temperature measuring wafer, a thickness thereof is 3 mm or less, and it is considerably difficult to form the storage chamber with the insulating material made of the nano-crystal silicon (nc-Si), and a cost thereof is increased. Meanwhile, recently, an A/D converting circuit, a memory, and a transmitting circuit that can be used under an atmosphere at about 250° C. have appeared due to improvement in an element material. Thus, it is not necessary to store the A/D converting circuit, the memory, and the transmitting circuit in the storage chamber, and the A/D converting circuit, the memory, and the transmitting circuit can be arranged on the temperature measuring wafer, or the A/D converting circuit, the memory, and the transmitting circuit can be formed directly on the temperature measuring wafer when they are thinned.
However, in order to activate the A/D converting circuit, the memory, and the transmitting circuit, a power supply is needed. However, there is no thin-film battery that can be used in a wide range of temperature of 150° C. or more to −100° C., so that the range of the suitable temperature of the wafer thermometer is limited by the usable temperature of the battery. In addition, it is thought that a dry cell or a rechargeable secondary cell is housed in a storage chamber having an insulating structure and used, but it is necessary to replace or charge the cell.